JPH06210423A - Manufacture of cast parts whose surface layer part is made of high alloy - Google Patents

Abstract

PURPOSE:To manufacture the cast parts whose surface layer part is made of high alloy by holding the temperature of the die at the prescribed calculated value, and forming the parts at the machining speed higher than the prescribed value. CONSTITUTION:The alloy stock in the solid-liquid coexistent condition is supplied to a die which is held at the temperature as indicated in the inequality, and the casting is formed at the machining speed of >=0.5m/sec. The alloy stock is Fe-C alloy or Al-Si-Cu alloy. When the material in the solid-liquid coexistent condition is formed, the part in the vicinity of the surface is made of high alloy, while the inside where the solid phase is mixed is made low alloy. That means, in the case of the steel where the material contains C, the surface layer part is made of steel containing more C, and the inside is made of steel containing less C. When the material is Al alloy containing Si and Cu, the surface layer part is made of Al alloy containing more Si and Cu, while the inside is made of Al alloy containing less Si and Cu. When the temperature of the die is low, only the liquid phase of the surface layer part is rapidly solidified to make high alloy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention proposes a method of manufacturing a cast part having a high alloy surface layer, which is suitable for use in gears, cams and the like which are required to have wear resistance.

[0002]

2. Description of the Related Art Parts such as gears and cams are usually manufactured by mechanically working a block-shaped steel material. In this case, the inside of the parts and the surface layer have the same composition. Therefore, in the case of parts that are particularly tough and require wear resistance, there is no steel material that can meet those requirements, so only the surface layer that requires wear resistance is highly alloyed, for example, by carburizing the surface layer. The carbon content of the steel is increased to make it harder, and the toughness is maintained while maintaining the carbon content of the steel material inside, making it a tough and wear-resistant component as a whole. However, there are problems that the carburizing process requires a long time, the carburized layer is thin, and when this part is worn, the wear rapidly progresses.

On the other hand, in the case of aluminum alloys, there is no industrial method for highly alloying only the surface layer.

[0004]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the above-mentioned problems in an advantageous manner, and as a completely new means, the surface layer portion formed by casting from a solid-liquid coexisting state is higher in alloy than the surface layer portion inside. It is an object of the present invention to propose a method for manufacturing a cast component of.

[0005]

According to the present invention, it is advantageous that the cooling condition at the time of supplying the material in the solid-liquid coexisting state to the mold to perform the molding affects the dispersion state of the solid phase in the solid-liquid mixed phase state. It was used for.

That is, the gist of the present invention is that an alloy material in a solid-liquid coexisting state is supplied to a mold held at a temperature (T _K ) shown in the following formula and is molded at a processing speed of 0.5 m / sec or more. A method for manufacturing a cast part having a high alloy surface layer.

[Equation 2] Is.

The above alloy materials are Fe--C type alloys,
Or an Al-Si-Cu based alloy,

Here, the term "casting" includes forging generally called molten metal forging (to be exact, casting).

[0009]

The background of the invention and its operation will be described. In the casting of a material in a solid-liquid coexisting state with a die, the material is heated to a temperature at which a part of the material melts and is molded. In such a material, when a part of it is molten, the liquid phase is held in the interstices of the solid phases that are connected in a net shape, and the material is solid as a whole and can be moved from the heating position to the mold. When applied, the reticulated solid phase is broken into fine fragments, which becomes a solid-liquid mixed phase suspended in the liquid phase and has the same fluidity as the liquid phase, and can fill the mold cavity.

According to this method, compared with molten metal casting, it can be formed at a lower temperature, and since the solidification latent heat is also small, the heat load on the die is small. For this reason, it becomes possible to die cast iron alloys that could not be die cast industrially due to the heat resistance of the mold in molten metal casting.

As a result of various attempts at die casting from such a solid-liquid coexisting state, the following findings were obtained.

When a material in a solid-liquid coexisting state is supplied into a mold and molded, only the liquid phase exists in the vicinity of the surface in the solid-liquid mixed phase state. In the case of hypoeutectic alloys, in the solid-liquid coexistence state, the liquid phase has a composition with a large additive content, and the solid phase has a composition with a small additive content. The interior where the phases are mixed is a low alloy. That is, the material is C
In the case of steel containing, the surface layer is a steel with a high C content, and the inside is C
If the content is steel, and if the material is an Al alloy containing Si and Cu, the surface layer part has a large amount of Si and Cu contents, and the inside is an Al alloy with a low content of Si and Cu.

When the mold temperature is low, the above-mentioned surface layer portion only in the liquid phase contacts the mold and solidifies rapidly. Therefore, a cast part having a high alloy in the surface layer and a low alloy in the inside can be obtained.

When the mold temperature is high, it takes time for the liquid phase only portion of the surface layer portion to come into contact with the die and to solidify. To the inside, the composition of the surface layer portion and the inside is made uniform.

When the mold temperature is low If the processing speed (in die casting: plunger speed = injection speed, in squeeze casting: punch (mold) pushing speed) is too slow, the temperature of the material will be reduced before the completion of molding. The fluidity is lowered and the mold cavity is not filled with the material. Based on these findings, the solid phase ratio (0.
3 temperature range target value component composition of the liquid phase at a temperature at which the selection) in the 0.8 (selected in the state diagram of the composition of the equal material to high alloy component composition) [Equation 2] (T _K By using the die of (1) and molding at a processing speed of 0.5 m / s or more, a high alloy cast part having a desired composition in the surface layer portion can be obtained.

The cast part manufactured by this method can have a high alloy in the surface layer portion up to about 1 mm from the surface.

[0017]

【Example】

Example 1 An Al alloy containing 4.5 mass% Cu was heated to a solid-liquid coexistence region at 626 ° C. (solid roughness rate: 0.7), supplied to a mold made of SKD61 having the dimensions shown in FIG. Situation, metallographic structure of cast parts and surface layer (within 1mm depth from the surface) and Cu inside
The content was investigated.

In FIG. 1, 1 is a casting part, 2 is an upper mold, 3 is a lower mold, and after the raw material is supplied to the lower mold 3, the upper mold 2 is immediately pushed to obtain a casting part 1. .

As the casting conditions, the pushing speed (working speed) of the upper mold 2 and the temperatures of the molds (upper and lower molds 2 and 3) were changed, and these conditions and investigation results are shown in Table 1.
Are shown together.

[0020]

[Table 1]

As is clear from Table 1, in the conforming examples of the present invention of Sample Nos. 1-1 and 1-2, the material filled the mold cavity, and the surface layer portion contained the additive component (Cu). While many high alloy cast parts have been obtained, sample No. 1-
In Comparative Examples 3 and 1-4, the mold cavity was not filled with the material due to the low processing speed, and the mold temperature was high, so that the surface layer part and the inside had a uniform structure. The component compositions of and have similar values.

In addition, the conformity example of sample No. 1-1 and sample No.
2 and 3 are metallographic photographs of Comparative Examples 1-3, respectively.
However, as is clear from these figures, the surface layer portion of FIG. 2 of the fitting example is only the solidified structure of the liquid phase,
FIG. 3 of the comparative example shows a solidified structure in a liquid phase and a solid-liquid mixed state both in the surface layer and inside. In FIGS. 2 and 3, the white portion is the solid phase in the solid-liquid coexisting state and is Cu.
The portion with a low content and appearing black is the liquid phase portion and the portion with a high Cu content.

Example 2 An alloy steel of 2.5 mass% C-0.5 mass% Si-0.5 mass% Mn was heated to a solid-liquid coexistence region at 1238 ° C. (solid phase ratio: 0.5), and was heated to 10
A die made of Cu-Cr-Zr alloy at 0 ° C was die-cast to produce a cast part having the dimensions shown in Figs. 4 (a) and 4 (b). Surface layer
(Within 1 mm from the surface) and C, Si and Mn inside
The content was investigated.

In FIG. 4 (a), 1 is a cast part, 4 is a gate, 5 is a runner, and 6 is a biscuit.
4 (b) is an explanatory view of the front of FIG. 4 (a).

As the casting conditions, the injection speed (processing speed) was changed, and these conditions and the survey results are summarized in Table 2.

[0026]

[Table 2]

As is clear from Table 2, in the sample Nos. 2-1 and 2-2 according to the present invention, the mold cavity was filled with the material, while in the sample No. 2-3, the comparative example had a processing speed. Since it is slow, the mold cavity is not filled with material.
Further, a metallographic photograph of a conforming example of Sample No. 2-1 is shown in FIG. 5, in which the surface layer has a solidified structure in a liquid phase and the inside has a solidified structure in a solid-liquid mixed phase. Also, the Mn content is larger in the surface layer portion than in the inside. In addition, about these, the conformity example of sample No2-2, sample No2-3
The comparative example showed the same tendency.

Example 3 An Al alloy of 9 mass% Si -2 mass% Cu was heated to a solid-liquid coexistence region at 551 ° C. (solid phase ratio: 0.5) and heated to 250 ° C. and made of SKD61 gold having the dimensions shown in FIG. It is supplied to the mold and processed at a processing speed (indentation speed of the upper mold 2) of 1 m / s, the molding situation, the metallographic structure of the cast part and the surface layer (1 mm depth from the surface).
Within) and internal Si and Cu contents were investigated.

As the casting conditions, the mold temperature was changed, and Table 3 shows the conditions and the survey results.

[0030]

[Table 3]

As is apparent from Table 3, in the conforming example of the present invention of sample No. 3-1, the surface layer portion is a solidified structure in the liquid phase and Si
And Cu content are also larger than in the inside, the comparative example of Sample No. 3-2 shows a solidified structure in a solid-liquid coexisting state in which the surface layer part and the inside are made uniform, and the Si and Cu contents are also the same. Indicates the value of.

[0032]

According to the present invention, when casting from a material in a solid-liquid coexisting state, by limiting the mold temperature and the processing speed, it is possible to improve the productivity of cast parts having a higher alloy in the surface layer than in the inside. Since it can be manufactured and can be applied to a wide range of component systems, the cast part according to the present invention can be advantageously used in applications where surface layer properties such as wear resistance are required.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing dimensional specifications of a mold used in Examples.

FIG. 2 is a photograph of a metal structure of a conforming example of the present invention.

FIG. 3 is a photograph of a metal structure of a comparative example.

FIG. 4 (a) is an explanatory diagram showing dimensional specifications of a cast component by die casting used in the examples. (b) is a description of the front view of (a).

FIG. 5 is a metallographic photograph of a conforming example of the present invention.

[Explanation of symbols]

 1 Cast parts 2 Upper mold 3 Lower mold 4 Gate 6 Runway 7 Biscuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuichi Ando 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture

Claims (3)

[Claims] 1. An alloy material in a solid-liquid coexisting state is supplied to a mold maintained at a temperature (T _K ) shown in the following formula, and a processing speed is 0.5 m.
A method for producing a cast part having a high alloy surface portion, characterized by being formed at a rate of / s or more. [Equation 1] 2. The method for manufacturing a cast component having a high alloy surface layer portion according to claim 1, wherein the alloy material is an Fe—C based alloy. 3. The method for producing a cast component having a high alloy surface layer portion according to claim 1, wherein the alloy material is an Al—Si—Cu alloy.